20150404-Care and Use of the Dumpy

[Type text] Care and Use of the Dumpy Data Date

07/04/2015

Page 1 of 7 Allan S Phillips

QA QC Coordinator

This guideline is directed towards the Care and Use of the Dumpy in order that we install mechanical equipment, pipes supports, structural steel foundation pads etc., to the correct level, the first time. All technicians are encouraged to use the dumpy to set levels for their own work. In fact it is a sign of competence; however if the technician uses the instrument without first checking to see that it will provide the correct readings; much time, effort and money is needlessly lost. By adhering to the following guidelines we decrease these risks. Index Item Description Page #

1 Storage and Handling of the Instrument

2 Calibration of the Instrument

3 How to carry out a site check to prove the instrument is ok to use

4 Correct Installation tips and techniques for the Tripod and dumpy.

5 Using a Log Book to record readings

6 Example of taking Readings

7 Here’s a useful Tip

8 Actual Report on the Incorrect set up of a dumpy


07/04/2015


QA QC Coordinator

1 Storage and Handling of the Instrument When the dumpy was purchased it came in a hard cased pack with an inner moulded to the shape of the dumpy. The case is weather tight when the clasps are closed. The case contains the dumpy plus instructions on the care, cleaning and lubrication plus how to make any adjustments that may be necessary from time to time. Read the Instructions, and always return the dumpy to the case for protection when stored. Most importantly the instrument comes with a calibration certificate, a test certificate stating the precision and tolerances when the unit left the factory. Always remember the dumpy is a precision instrument comprising optical lens and refracting prisms. With adjusting screws to align and focus. Take good care of the unit and it will serve you well for years. If you should happen to drop it or seriously bump it, report it to the Quality Department who will arrange to have the unit recalibrated. 2 Calibration of the Instrument Make sure that the instrument has a current calibration certificate before you use it. The QA section of the organisation you work for keeps a register of all instruments. If you find that the instrument is outside the calibration period, return it to the stores as the instrument has to be returned to the manufacturer for checking and recalibration. . 3 How to carry out a site check that the instrument is ok to use Find two columns about 30-40 meters apart Set up the dumpy about 10 meters from one column (no need to measure it –roughly ¼ of the distance is just fine. Tape an A3 sheet of paper on to the column at the same height as your instrument Draw a squiggly line down though the page so that you can see the line vertically from your instrument. When you can see the level draw a horizontal line with a pencil on the A3 paper. Now do the same to the other column – Tape on an A3 Sheet of paper – draw a squiggly line up and down the sheet. Go back to the dumpy and adjust the eyepiece so that you can clearly see the RL Line and draw that line on the paper. Now break down the instrument and re setup the instrument this time about ¼ the distance from the opposite column. Go through the same procedure of locating the RL then draw the line horizontally across the sheet. Same thing with the sheet on the opposite column. Now take both sheets off and lay one on top of the other, The lines must be the same distance apart. If they are your instrument is reading correctly. With practise and confidence you will carry out the exercise on the steel columns near the actual job you are about to work on. You mark both lines on both columns in the same way you would on paper. Use a steel rule and measure both columns you must have the same distance to be sure the instrument is reading correctly.


07/04/2015


QA QC Coordinator

4 Correct Installation tips and techniques for the Tripod and dumpy

First set the tripod with three legs apart at a comfortable height. Pick a spot about 20 meters from the job, same distance from the Bench Mark you will be using. Make sure the tripod is well out of harm’s way and will not interfere with ongoing works, vibrating rollers, busy workers etc. Press the tripod legs firmly in to the ground, place weights on the purpose lugs if setting up on hard concrete. Set the oval shaped head approximately level, take out the dumpy and attach to the head with the knurled screw under. Do not over tighten just a firm finger action to tighten is all that’s needed.


07/04/2015


QA QC Coordinator

Knurled Screw to connect the Dumpy Press the Tripod legs firmly into the ground

Look at the Bullseye Vial and adjust the three screws until the bubble sits inside the inner circle. Now rotate the instrument 180 degrees and readjust the three screws to keep the bubble inside the inner circle. Check once again by rotating the dumpy another 180 deg. Using the rifle sight roughly point the instrument towards the job then use the adjustment shown on the RH Side then the knurled ring closest to your eye to bring the job in to focus. If you do not have an assistant to hold the staff, lean the staff as close to vertical as you can and adjust the inner ring screw so that the focus is clear and you can see a vertical line plus three horizontal lines. The Middle line is the important one (the upper and lower stadia lines are for recording distances) we are dealing with levels.


07/04/2015


QA QC Coordinator

Use the three adjusting screws to set the instrument level – check with the Bullseye Vial If you have trouble reading the staff, a tape rule attached to a strong stick will do the same job, but try to familiarise yourself with the staff, it becomes easier with practise. The staff comes with a detachable spirit level that your assistant should use to keep the staff vertical whenever you take a reading. Take a backsight on a known Benchmark, in your log levels book write down the BM Id and the level. Read the staff, write down the reading in your book, add the two figures and you now know the RL Relative level of your instrument. Set the staff directly over the work and take any readings you may need identify each one and write down the readings in you book. Always close out your work by making the last reading the same as the first one on the bench mark. When you have made the additions or deletions to establish RL rise and fall if required you should always end up with the same RL as you started with. We call this a close out. The following sketch will help to clarify these instructions.


07/04/2015


QA QC Coordinator

Backsight Intermediate Foresight Rise Fall RL

First

Reading Last

Reading

Stn BS IS FS Rise Fall RL Remarks

BM S19 7766 Bench Mark #

S19

Ins 260 8026 Instrument

TOC 3311 3051 4715 Top of Concrete

Pin 1312 1999 6714 set out pin

TOC 2500 1188 5526 Top of Concrete

+Bolts 2400 100 5626 top of bolts

BM S19 260 2140 7766 Close

Sketches

7 Here’s a useful Tip Do as much of your prep work, making sketches, chasing down the BM to use, reviewing the construction drawings before you go out to use your dumpy. Talk to any Surveyor and ask him just how much time does he spend putting the design data in to his model. They already have the necessary data logged in before going out to survey, that’s how they can tell you that a fixture requires adjusting 10mm North 5 mm East for example on the spot . They already have the correct location set in to their data base by loading the information in to the computer before taking any actual readings. You can do much the same thing by collecting all available data in to your work pack, BEFORE TAKING READINGS...


07/04/2015


QA QC Coordinator

Now for the most important tip of all. Every one of us who set levels has at some time added a figure when we should have subtracted. We usually do this when rushed, with a work crew anxiously waiting for our reading. So the lesson to be followed is a) always use some quiet time to go through your own work. Set your work sketches out clearly so

that any one checking your work can follow through on the logic. And secondly b) ALWAYA ALWAYS ALWAYS have someone check your work.

8 Actual Report on the Incorrect set up of a dumpy Being aware that there are reported discrepancies with As Constructed Levels established by Registered Surveyors and the findings of SMP team members when using a dumpy level, I reviewed one set up and use of a dumpy level by a SMP Team and find that the equipment (dumpy level) was established in a manner most likely to give level errors. The establishment of the Tri-Pod did not follow common practise. The three legs were Simply placed on a gravel base, not securely fixed and locked. One leg was established close to a loose embankment, the tri-pod location was only just clear of the work access pathway. The dumpy was set level using the bulls eye vial, however the compensator was not checked, nor any pre work checks for cross hair level readings.

Tri-Pod is resting on the gravel base, close to a busy passage way – with one leg (LH Side) sitting close to a loose embankment.

The Tri-Pod legs have purpose built in lugs for the operator to strike with his heel, thereby securing and protecting the tri-pod from unwanted disturbance.

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20150404-Care and Use of the Dumpy